Field of the Invention
The present invention relates to an aqueous ink, an ink cartridge, and an ink jet recording method.
Description of the Related Art
An ink jet recording method allows images to be recorded on various recording media. In addition, in order to obtain a more satisfactory image, there have been proposed various inks in accordance with purposes, such as an ink suitable for recording an image of photographic quality on glossy paper or the like, and an ink suitable for recording a document on plain paper or the like.
In recent years, with use of plain paper or the like as a recording medium, the ink jet recording method has also been utilized for recording of, for example, a business document containing characters, diagrams, and the like, and frequency of its use in such application has been markedly increasing. In such application, it is important that an image having a black color tone, such as a character or a diagram, can be output with a high density, and an ink containing a self-dispersible pigment as a colorant is often utilized.
Various proposals concerning the self-dispersible pigment have heretofore been made. For example, there is a proposal of a modified pigment having a carboxylic acid group bonded via another atomic group to a particle surface of the pigment (Japanese Patent Application Laid-Open No. H10-510862). In addition, there are also proposals of various oxidized type self-dispersible pigments each having a carboxylic acid group directly bonded to a particle surface of the pigment (Japanese Patent Application Laid-Open No. 2003-535949, Japanese Patent Application Laid-Open No. 2012-117020, Japanese Patent Application Laid-Open No. H08-003498, and Japanese Patent Application Laid-Open No. 2010-254765).